Shale gas has been a “game changer” in the US, where it has caused gas prices to plummet and is already providing more than a third of current gas consumption.

But on an island like the UK reserves are much smaller and more difficult to access.

Mr Davey accused those on the right of the Tory party of making out the UK could rely on shale gas in order to undermine investment in alternatives such as offshore wind.

“The right wing of tory party are trying to make out shale gas is the answer but I’m afraid the evidence does not bear it out,” he said.

However he did make clear that shale gas could still be useful to the UK, providing up to 10 per cent of energy needs, and is expected to give fracking the go-ahead in the next few weeks following a consultation which has just ended.

“Centrica and Shell say that if we exploited all the shale gas that is there we should have five per cent maybe 10 per cent of energy needs,” he added.

The Department of Energy and Climate Change are currently working with the British Geological Survey to carry out a definitive survey of how much shale gas is under the UK.

At the moment the BGS estimate there is 5.3 trillion cubic feet (150 billion cubic metres), around two year’s worth of the UK gas consumption needs, but admit with such an unconventional resource “we simply do not know”.

Shale gas is extracted by blasting water, sand and chemicals at extreme pressures to release gas trapped deep in rock, a technology known as fracking.

The process can cause earthquakes and contamination of water supplies if gas leaks into groundwater reserves.

Environmentalists fear that if fracking takes off in the UK then communities will be in danger from water pollution and earthquakes.

The biggest UK reserve is around Blackpool, where exploratory wells have already been dug and earthquakes have been caused.

Cuadrilla UK estimate there could be as much as 200 trillion cubic feet in this reserve alone, 40 times the BGS estimate and enough to meet UK gas needs for 80 years.

But Stephen Smith, a spokesman for the company, admitted that just five to 15 per cent was likely to be accessible for extraction.

“Nobody on either side has said it would transform Britain. It is part of the mix it is not the thing that will transform things,” he said.

Professor Richard Davies, Director of Durham Energy Institute, Durham University, said shale gas could prove useful to the UK energy security because it can be accessed at any time.

However he pointed out that it remains an expensive and relatively unproven technology, with questions remaining over disposing of the waste water and the long term effect on geology.

It is also very unclear even in the US how much shale gas there is because it is not really possible to accurately assess until a number of wells have been drilled.

“The problem with the UK is it does not have large sedimentary basins and we have a large population.

The US has a huge glut of shale gas and as a consequence at the moment it is very cheap.

“In the UK it could help us a bit with energy security, so we are not so reliant on foreign gas but the UK is not going to be the strongest shale gas developer.”